The long-range purpose of the project is to study the biochemistry, morphology, pharmacology and physiology of inner ear neurons and cells and of their interactions and to describe the mechanisms of these interactions. The interest is now focused on: 1) refinement of techniques for assaying carbonic anhydrase isoenzymes in cochlear samples and other tissues; refinement of techniques for total micro amino acid analysis of picomole quantities of the vascular stria of the cochlea of guinea pigs; 2) a morphological study of the ultrastructure of membranes of the inner ear, particularly of the regional specialization of the hair cell plasmalemma in the organ of Corti; 3) a physiological study of synaptic transmission in the inner ear, showing that alpha-bungarotoxin reversibly blocks synaptic transmission of crossed olivocochlear nerve fibers, strengthening the hypothesis that these fibers are cholinergic.